Recently, interests in energy storage technology have been gradually increased. As the application field of energy storage technology is enlarged to energy for cellular phones, camcorders, notebook computers and electric vehicles, efforts on the research and development of electrochemical devices are increasingly embodied. In this aspect, the field of electrochemical devices have received the majority of attention, and among them, interests in the development of chargeable/dischargeable secondary batteries are focused. Recently, in order to increase the capacity density and specific energy in developing such batteries, research and development for the design of new electrodes and batteries have been conducted.
Among secondary batteries which are currently applied, lithium secondary batteries developed in the early 1990s are in the spotlight due to the advantages of higher operation voltages and far greater energy densities than those of conventional batteries, such as Ni—MH, Ni—Cd and sulfuric acid-lead batteries, which use an aqueous electrolyte solution.
In general, lithium secondary batteries are constructed by embedding an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode in the form of a stacked or wound structure in a battery case and injecting an electrolyte therein.
In this case, when a lithium electrode is used as the negative electrode, the lithium electrode formed by attaching a lithium foil on a planar current collector has been generally used.
FIG. 1 is a view illustrating electron transfer pathways in a lithium electrode prepared by attaching a lithium foil on a planar current collector in the related art.
If the above-described general lithium electrode 10 is described with reference to FIG. 1, when a battery is driven, electrons being transferred to a lithium foil 12 through a current collector 11 are transferred in a unidirectional flow. For this reason, electron density on lithium surface becomes non-uniform, and accordingly, lithium dendrites may be formed.
These lithium dendrites may finally cause damage to the separator and may generate a short circuit in the lithium secondary battery, and as a result, there may occur a problem in that the safety of the lithium battery deteriorates.